title: Kinetics of the H+-ATPase from dry and 5-hours-imbibed maize embryos in its native, solubilized, and reconstituted forms.
abstract: Membranes undergo recovery upon rehydration in seed germination. Previous work has described that the plasma membrane H+-ATPase from maize embryos adopts two different forms at 0 and 5 h of imbibition. We investigated how the kinetics of these two forms could be affected by alterations in the plasma membrane (PM). In comparison to the 0-h, PMs from the 5-h imbibed embryos showed changes in glycerophospholipid composition, decrease in leakage, and increase in fluidity. Kinetics of the PM H+-ATPase from 0 and 5-h imbibed embryos showed negative cooperativity. With the removal of the membrane environment, the activity of the enzymes shifted to a more complex kinetics, displaying two enzyme components. Lipid reconstitution produced one component with positive cooperativity. In all cases, enzymes from 0 and 5-h imbibed embryos presented similar kinetics with some quantitative differences. These results indicate that the two enzyme forms have the potential ability to respond to changes in the membrane environment, but the fact that they do not show differences in the native membranes at 0 or 5 h implies that modifications in the membrane are not drastic enough to alter their kinetics, or that they are able to preserve their boundary lipids or associated proteins and thus retain the same kinetic behavior.
authors.affiliation: Departamento de Bioquímica, Facultad de Química, Conjunto E. Universidad Nacional Autónoma de México, Cd Universitaria, 04360 México, DF México.
authors.forename: Sobeida
authors.initials: S
authors.lastname: Sánchez-Nieto
authors.forename: Consuelo
authors.initials: C
authors.lastname: Enríquez-Arredondo
authors.forename: Fernando
authors.initials: F
authors.lastname: Guzmán-Chávez
authors.forename: Rolando
authors.initials: R
authors.lastname: Hernández-Muñoz
authors.forename: Jorge
authors.initials: J
authors.lastname: Ramírez
authors.forename: Marina
authors.initials: M
authors.lastname: Gavilanes-Ruíz
mesh_terms: D002462:Cell Membrane / Q000201:enzymology; D003890:Desiccation; D007700:Kinetics; D008055:Lipids / Q000737:chemistry; D008954:Models, Biological; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D012639:Seeds / Q000201:enzymology*; D012995:Solubility; D013379:Substrate Specificity; D013997:Time Factors; D003313:Zea mays / Q000196:embryology* / Q000201:enzymology*
chemical_list: D008055:Lipids; D006180:Proton-Translocating ATPases